CN111794221A - Prestressed anchor cable construction method - Google Patents

Abstract

The application relates to a construction method of a prestressed anchor cable, which comprises the following steps: step S1: forming holes, including construction paying-off, drill positioning, drilling, hole sweeping and final hole inspection and acceptance; step S2: filling heated crushed slag into the drilled hole, wherein the hole walls at different depths are filled with the heated crushed slag; step S3: manufacturing and installing an anchor cable, and putting the anchor cable into the hole; step S4: grouting, and carrying out secondary grouting on the holes; step S5: constructing the enclosing purlin, leveling a concrete enclosing purlin construction substrate by adopting 5cm cement mortar, and then manufacturing and installing reinforcing steel bars; step S6: constructing an anchor head; step S7: a backing plate, wherein a steel pipe matched with the diameter of the drilled hole is used for welding the complete cylinder pad; step S8: and tensioning and locking, namely performing tensioning and locking operation after grouting of the anchor cable and construction of the anchor head and maintaining for 2-3 days. This application has the effect that improves the intensity of prestressed anchorage cable pouring cement mortar posthardening in the wet cold soil property.

Description

Prestressed anchor cable construction method

Technical Field

The application relates to the field of engineering construction, in particular to a construction method of a prestressed anchor cable.

Background

During construction of deep foundation pits and side slopes of modern construction engineering, temporary or permanent support structures are often required to ensure structural stability of the slope protection, and anchor rod support is widely applied to the field of foundation pit and slope support as a tension structure body.

In the related art, anchor rods or prestressed anchor cables are supported by providing tension mainly through friction force generated between anchor rod bodies and soil bodies formed by grouting in drill holes.

In the related art, since the environment of the prestressed anchor cable drilling may be high in soil moisture and cold, the volume of water in soil at low temperature increases by about 9% at the time of freezing before hardening after grouting, and at the same time, an ice expansion stress of about 2500kg/cm2 is generated. This stress value is often greater than the initial strength value developed within the set cement, causing the concrete to fail to varying degrees (i.e., early freezing failure) and reduce strength. In addition, after water turns into ice, crystals with larger particles are generated on the surfaces of the aggregates and the steel bars, so that the bonding force of cement paste with the aggregates and the steel bars is weakened, and the compressive strength of concrete is influenced. When the ice melts, various gaps are formed in the concrete, so that the compactness and durability of the concrete are reduced. Therefore, in winter concrete construction, the form change of water is the key to influence the strength increase of concrete.

Therefore, the inventor believes that the related art of prestressed anchor cable construction still has a defect in the hardening strength of cement mortar after pouring in the case of high soil moisture and cold weather.

Disclosure of Invention

In order to improve the strength of hardening after pouring cement mortar into the prestressed anchor cable in the wet and cold soil, the application provides a prestressed anchor cable construction method.

The construction method of the prestressed anchor cable provided by the application adopts the following technical scheme:

a construction method of a prestressed anchor cable comprises the following steps: step S1: drilling, including construction paying-off, drilling machine positioning, drilling, hole sweeping and final hole inspection and acceptance; step S2: filling heated crushed slag into the drilled hole, wherein the hole walls at different depths are filled with the heated crushed slag; step S3: manufacturing and installing an anchor cable, and putting the anchor cable into the hole; step S4: grouting, and carrying out secondary grouting on the holes; step S5: constructing the enclosing purlin, leveling a concrete enclosing purlin construction substrate by adopting 5cm cement mortar, and then manufacturing and installing reinforcing steel bars; step S6: constructing an anchor head; step S7: a backing plate, wherein a steel pipe matched with the diameter of the drilled hole is used for welding the complete cylinder pad; step S8: and tensioning and locking, namely performing tensioning and locking operation after grouting of the anchor cable and construction of the anchor head and maintaining for 2-3 days.

By adopting the technical scheme, the slag heated in the step S2 can not only heat the hole and has water absorption property, water in the hole is absorbed, so that the temperature of the hole wall is increased, the dryness of the hole wall is improved, in the step S4, the temperature of the hole wall enables the cement to hydrate and release heat quickly, the cement is solidified and accelerated, the increasing rate of the strength of the cement is accelerated due to the higher temperature in the hole, and the ice in the cement is reduced, so that the gaps in the cement are reduced, and the strength of the cement is improved.

Preferably, in step S2, the heated crushed slag is obtained by crushing the burnt coal cake or charcoal, and the diameter of the crushed slag is controlled to be 60mm to 80 mm.

By adopting the technical scheme, the briquette and the charcoal are low in cost and convenient to fire, have good water absorption, can absorb water in cement when being mixed with the cement poured into the briquette, and accelerate the cement solidification.

Preferably, in step S2, the method for filling the hole walls with different depths with the heated slag includes: the heated slag is placed in the hole opening in times and poked into the hole walls with different depths through a long pipe.

Through adopting above-mentioned technical scheme, poke the pore wall of the different degree of depth with the disintegrating slag of heating, make the different degree of depth in the hole all can be heated and dry.

Preferably, in step S2, when the moisture content in the pores is high, quicklime powder is added to the briquette or charcoal when the heated crushed slag is fired.

By adopting the technical scheme, the quicklime powder has water absorption and can absorb moisture in the hole wall, the alkalinity in the hole can be improved, and the setting speed of cement is improved.

Preferably, the step S4 specifically includes the following steps: a. grouting for the first time: the anchor cable and the steel strand are simultaneously placed at the bottom of the hole, the distance between the pipe orifice and the bottom of the hole is 150mm, so that slurry is discharged, the specification of the slurry adopts cement mortar with the ash-sand ratio of 0.5-1.0 and the water-cement ratio of 0.38-0.45, and the cement adopts No. 42.5 ordinary portland cement; before grouting, grouting can be carried out on the pipeline after the pipeline is checked without blockage, the grouting speed is controlled to be about 100L/min, the grouting pressure is controlled to be 0.5-1.5 MPa, and the 1 st grouting is completed when slurry and impurities in the hole are replaced by cement slurry and overflow from the hole opening; b. grouting for the 2 nd time: and (3) after the grout for the 1 st time reaches the initial setting strength, grouting for the 2 nd time, wherein the grouting grout adopts pure cement grout with the water cement ratio of 0.45-0.50, and a proper amount of early strength agent is added if necessary.

By adopting the technical scheme, the secondary grouting reduces gaps in cement and improves the strength of the hardened cement.

Preferably, when the cement mortar is prepared by mixing before grouting in step S4, the cement mortar is mixed using hot water of 50 to 70 ℃.

By adopting the technical scheme, the hydration speed of the cement can be fast by stirring with hot water, the hydration speed is accelerated along with the rise of the temperature, and the setting time is shortened.

Preferably, the construction of the anchor head in step S6 follows the following rules: a. the anchorage device and the base plate are coaxially arranged with the anchor cable body, and the axial angle deviation of the anchor cable body after being locked is less than or equal to +/-5 degrees. (ii) a b. The contact surface of the base plate and the pad pier is ensured not to have any gap; c. cutting redundant anchor cable bodies of the anchor head by adopting a cold cutting method, wherein the reserved length outside the anchor is more than or equal to 5 cm; d. when tension needs to be compensated, the tension length needs to be considered to be reserved; e. the anti-corrosion treatment of the anchor head should be in compliance with the regulations.

By adopting the technical scheme, the quality of the anchor head is ensured.

Preferably, the step S8 stretch-draw locking must meet the following process quality requirements: a. leveling the support component surface of the bearing plate before tensioning, installing the bearing plate, the base plate and the anchorage device, keeping the bearing plate, the base plate and the anchorage device to be vertical to the axis direction of the anchor rod, and keeping the axis of the jack to be coincident with the axis of the anchor cable as much as possible when the jack is installed; b. the jack and the high-pressure oil pump are calibrated before installation, tensioning is carried out according to calibrated data, and the working condition of the high-pressure oil pump and the smooth condition of an oil pipe are checked in advance so as to avoid tensioning failure caused by abnormal working of the oil pump during tensioning; c. tensioning is carried out according to a certain program, and the tensioning sequence of the anchor cables is determined by considering the mutual influence on the adjacent anchor cables; d. the anchor cable is pre-tensioned for 2 times before formal tensioning, and the tensioning force is 0.1-0.2 times of the design load, so that the tight contact of all parts of the anchor cable and the flatness of the rod body are ensured, and the hidden deformation of the rod body is eliminated. When stretching is carried out after straightening, the starting point of the deformation amount is recorded by taking the state as a zero point; e. controlling the tension control stress within the range of 0.65-0.75 times of the standard value of the anchor cable strength; f. tensioning loads are applied step by step in a graded mode, the loads are increased to 1.05 times of design loads through the last tensioning, the loads are observed for 10-15 min, if deformation is unchanged, the anchor cable is kept in an original state, a pointer of a pressure gauge on the oil pump does not return, the design loads can be unloaded, and locking operation is carried out; g. the locking operation must be strictly performed according to the standard, and after the anchor cable is locked by using a standard anchorage device, if obvious prestress loss is found, tensioning compensation is performed.

By adopting the technical scheme, the tensioning locking meets the process quality.

In summary, the present application includes at least one of the following beneficial technical effects:

the slag heated in the step S2 can not only heat the holes, but also have water absorption property, and adsorb water in the holes, so that the dryness of the hole walls is improved while the temperature of the hole walls is increased, so that in the grouting process in the step S4, the temperature of the hole walls enables the cement to hydrate and release heat quickly, the cement solidification is accelerated, the increase rate of the cement strength is accelerated due to the higher temperature in the holes, and the icings in the cement are reduced, thereby reducing the gaps in the cement and improving the strength of the cement.

Drawings

FIG. 1 is a block flow diagram of a method of the present application.

Detailed Description

The present application is described in further detail below with reference to fig. 1.

The embodiment of the application discloses a construction method of a prestressed anchor cable. Referring to fig. 1, the construction method of the prestressed anchor cable includes the steps of:

step S1: forming holes:

a. the anchor cable drilling hole mainly contains: construction paying-off, positioning of a drilling machine, drilling, hole sweeping, final hole inspection and acceptance and the like, wherein a hole is formed by adopting a pipe following drilling mode of an anchor rod drilling machine, an alloy drill bit is flushed with water to drill, and the aperture phi is 150 mm.

b. The drilling machine is positioned and centered, the incident angle is adjusted (30 degrees), after the positioning and the rechecking are carried out, the drilling machine is started to drill, and the requirements of accuracy, flatness and stability are met in the drilling process; the drilling depth is required to be increased by 0.4m compared with the design depth, so that the residue which cannot be returned is deposited, and the depth of the anchor rod is ensured to meet the design requirement.

c. When the anchor cable is drilled, the horizontal allowable deviation among the holes is +/-10 mm, the vertical allowable deviation is +/-50 mm, the inclination allowable deviation of the drilled holes is 3 per mill, the final hole depth is preferably 40cm greater than the designed hole depth, the holes are thoroughly cleaned after the final holes, and clean water is utilized for circular flushing on a construction site; and after the inspection and acceptance are qualified, inserting the anchor cable for grouting construction.

Step S2: and filling heated slag into the drilled hole, wherein the hole walls with different depths are filled with the heated slag. Wherein, the heated crushed slag can be obtained by crushing burnt coal cakes or charcoal, and the diameter of the crushed slag is controlled to be 60-80 mm so as to facilitate the crushed slag to roll in the hole. Filling the disintegrating slag into the hole, adopting the mode of putting into in grades, placing the disintegrating slag of heating in the drill way in grades, poking the pore wall of the different degree of depth into through the long tube to pound the disintegrating slag to pieces with the long tube, receive stifled when avoiding being in milk. When the water content in the pores is high, quicklime powder is added to the briquette or charcoal during firing of the heated slag.

Step S3: anchor cable manufacture and installation:

the anchor cable is composed of phi 15.20 steel strands, and the steel strands fy = 1860N/mm.

The anchor cable manufacturing process can meet the following technical requirements:

a. the blanking length is controlled within 50mm according to the design hole depth, the waist beam (0.50 m), the steel base plate (0.057 m), the jack working length (0.4 m) and the jack working length (0.30 m), and the length deviation of each strand is cut by cold cutting.

b. The anchor bundle is provided with a bundle of wire loops (localizers) at intervals of 3m along the axial direction, an isolation frame is arranged between two bundles of wire loops at the anchoring section, the tensioning section is wrapped by a plastic sleeve, and the pipe orifice at the intersection of the tensioning section and the anchoring section is sealed and tied firmly by an iron wire;

c. a certain gap is ensured among the steel wires so as to ensure that the gap in the anchor bundle is fully filled after grouting, and the steel wires and the rod body are fully wrapped and protected;

d. the grouting pipe is a plastic pipe and is inserted into the center of the wire binding ring or the isolation frame;

e. when arranging the steel strand, 2 grouting pipes are simultaneously arranged for the 1 st grouting and the 2 nd grouting respectively, the grouting pipes for the 2 nd grouting are drilled with a pair of phi 6 through holes at intervals of 0.5m in the anchoring section, and the phi 6 through holes and the grout outlet are wrapped by adhesive tapes.

Step S3 further includes anchor cable installation and transportation:

after the steel strand is combined into a cable and the hole is drilled, the hole wall is cleaned before installation, the hole wall is determined to have no adhesive slurry, the type and specification of the steel strand material and whether the quality of each part meets the design requirement are rechecked, and then the anchor cable is lifted and slowly placed into the hole to the designed depth.

In the process of putting in, the device is strictly prohibited from shaking up and down, twisting back and forth and impacting, and the device is prevented from being loose and blocked midway to cause installation failure.

And 4, step 4: grouting:

and after the anchor cable is installed, grouting is carried out after the acceptance of the anchor hole and the steel strand is qualified. Because the construction environment temperature is lower, in order to accelerate the hydration speed of the cement and shorten the setting time, hot water of 50-70 ℃ is used for stirring cement mortar when the cement is prepared.

a. The 1 st grouting

The anchor cable and the steel strand are simultaneously placed at the bottom of the hole, and the distance between the pipe orifice and the bottom of the hole is 150mm, so that slurry is discharged. The specification of the slurry adopts cement mortar with the sand-lime ratio of 0.5-1.0 and the water-cement ratio of 0.38-0.45, and the cement adopts No. 42.5 ordinary portland cement. Before grouting, grouting can be carried out on the pipeline after the pipeline is inspected without blockage, the grouting speed is controlled to be about 100L/min, the grouting pressure is controlled to be 0.5-1.5 MPa, and the 1 st grouting is completed when slurry and impurities in the hole are replaced by cement slurry and overflow from the hole opening.

b. And (3) performing the 2 nd grouting after the 1 st grouting slurry reaches the initial setting strength, wherein the 2 nd grouting slurry is pure cement slurry with the water cement ratio of 0.45-0.50. If necessary, a proper amount of early strength agent (such as triethanolamine) is added.

Step S5: construction of purlin

The concrete purlin construction substrate is firstly leveled by adopting 5cm cement mortar, then steel bars are manufactured and installed, steel bar joints need to be staggered, the number of the steel bar joints on the same section does not exceed 1/2 of the total number of the steel bars, and the distance between sections with welded joints is not less than 1 m. The template adopts a small steel template, and around the anchor hole, the reinforcing steel bars are dense and must be carefully vibrated to ensure the quality.

And step S6, construction of an anchor head:

the anchor head construction should follow the following regulations:

a. the anchorage device and the base plate are coaxially arranged with the anchor cable body, and the axial angle deviation of the anchor cable body after being locked is less than or equal to +/-5 degrees.

b. It should be ensured that the contact surface of the backing plate and the pad pier does not have any gap.

c. And cutting redundant anchor cable bodies of the anchor head by adopting a cold cutting method, wherein the external retention length of the anchor is more than or equal to 5 cm.

d. When compensation for tension is required, the remaining tension length should be considered.

e. The anti-corrosion treatment of the anchor head should be in compliance with the regulations.

Step S7: backing plate:

the anchor cable backing plate is generally made of a common steel plate, the shape of the anchor cable backing plate is square, the size and the thickness of the anchor cable backing plate are determined by the size of anchoring force, and in order to ensure that the plane of the backing plate is perpendicular to the axis of the anchor cable and improve the bearing capacity of a pad pier, a steel pipe matched with the diameter of a drilled hole is generally welded into a sleeve backing plate.

Step S8: tensioning and locking:

after anchor cable grouting and anchor head construction are finished, after maintenance is carried out for 2-3 days (the cement strength reaches more than 90%), tensioning locking operation can be carried out, and the operation needs to meet the following process quality requirements:

a. leveling the support member surface of the bearing plate before tensioning, mounting the bearing plate (concrete waist beam), a base plate and an anchor, keeping the bearing plate, the base plate and the anchor vertical to the axis direction of the anchor rod, and keeping the axis of a jack to be coincident with the axis of the anchor cable as much as possible when the jack is mounted;

b. the jack and the high-pressure oil pump are calibrated before installation, tensioning is carried out according to calibrated data, and the working condition of the high-pressure oil pump and the smooth condition of an oil pipe are checked in advance so as to avoid tensioning failure caused by abnormal working of the oil pump during tensioning;

c. tensioning is carried out according to a certain program, and the tensioning sequence of the anchor cables is determined by considering the mutual influence on the adjacent anchor cables;

d. the anchor cable is pre-tensioned for 2 times before formal tensioning, and the tensioning force is 0.1-0.2 times of the design load, so that the tight contact of all parts of the anchor cable and the flatness of the rod body are ensured, and the hidden deformation of the rod body is eliminated. When stretching is carried out after straightening, the starting point of the deformation amount is recorded by taking the state as a zero point;

e. controlling the tension control stress within the range of 0.65-0.75 times of the standard value of the anchor cable strength;

f. the tension load is applied step by step. The load is increased to 1.05 times of the design load by the last tensioning, the load is kept for observation for 10-15 min, if the deformation is unchanged, the anchor cable is kept in an original state, and a pointer of a pressure gauge on the oil pump does not return, so that the design load can be unloaded, and locking operation is carried out;

g. the locking operation must be strictly performed according to the standard, and after the anchor cable is locked by using a standard anchorage device, if obvious prestress loss is found, tensioning compensation is performed.

The implementation principle of the construction method of the prestressed anchor cable in the embodiment of the application is as follows: the slag heated in the step S2 can not only heat the holes, but also have water absorption property, and adsorb water in the holes, so that the dryness of the hole walls is improved while the temperature of the hole walls is increased, so that in the grouting process in the step S4, the temperature of the hole walls enables the cement to hydrate and release heat quickly, the cement solidification is accelerated, the increase rate of the cement strength is accelerated due to the higher temperature in the holes, and the icings in the cement are reduced, thereby reducing the gaps in the cement and improving the strength of the cement.

The above embodiments are preferred embodiments of the present application, and the protection scope of the present application is not limited by the above embodiments, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.

Claims (8)

1. A construction method of a prestressed anchor cable is characterized by comprising the following steps:

step S1: forming holes, including construction paying-off, drill positioning, drilling, hole sweeping and final hole inspection and acceptance;

step S2: filling heated crushed slag into the drilled hole, wherein the hole walls at different depths are filled with the heated crushed slag;

step S3: manufacturing and installing an anchor cable, and putting the anchor cable into the hole;

step S4: grouting, and carrying out secondary grouting on the holes;

step S5: constructing the enclosing purlin, leveling a concrete enclosing purlin construction substrate by adopting 5cm cement mortar, and then manufacturing and installing reinforcing steel bars;

step S6: constructing an anchor head;

step S7: a backing plate, wherein a steel pipe matched with the diameter of the drilled hole is used for welding the complete cylinder pad;

step S8: and tensioning and locking, namely performing tensioning and locking operation after grouting of the anchor cable and construction of the anchor head and maintaining for 2-3 days.

2. The prestressed anchor rope construction method as claimed in claim 1, wherein the heated crushed slag is obtained by crushing a burned coal cake or charcoal, and the diameter of the crushed slag is controlled to be 60mm to 80mm at step S2.

3. The prestressed anchor rope construction method according to claim 1, wherein in step S2, the method for filling heated slag into the hole walls of different depths is as follows: the heated slag is placed in the hole opening in times and poked into the hole walls with different depths through a long pipe.

4. The prestressed anchor rope construction method as claimed in claim 2, wherein in step S2, when the moisture content in the pores is high, quicklime powder is added to the briquettes or charcoal when the heated slag is burned.

5. The prestressed anchor cable construction method according to claim 1, wherein the step S4 specifically includes the steps of:

a. grouting for the first time: the anchor cable and the steel strand are simultaneously placed at the bottom of the hole, the distance between the pipe orifice and the bottom of the hole is 150mm, so that slurry is discharged, the specification of the slurry adopts cement mortar with the ash-sand ratio of 0.5-1.0 and the water-cement ratio of 0.38-0.45, and the cement adopts No. 42.5 ordinary portland cement; before grouting, grouting can be carried out on the pipeline after the pipeline is checked without blockage, the grouting speed is controlled to be about 100L/min, the grouting pressure is controlled to be 0.5-1.5 MPa, and the 1 st grouting is completed when slurry and impurities in the hole are replaced by cement slurry and overflow from the hole opening;

b. grouting for the 2 nd time: and (3) after the grout for the 1 st time reaches the initial setting strength, grouting for the 2 nd time, wherein the grouting grout adopts pure cement grout with the water cement ratio of 0.45-0.50, and a proper amount of early strength agent is added if necessary.

6. The prestressed anchor rope construction method of claim 1, wherein the cement mortar is mixed with hot water of 50-70 ℃ while the cement mortar is mixed and prepared before grouting at step S4.

7. The prestressed anchor rope construction method as claimed in claim 1, wherein the construction of the anchor head in step S6 follows the following rules:

a. the anchorage device and the base plate are coaxially arranged with the anchor cable body, and the axial angle deviation of the anchor cable body is less than or equal to +/-5 degrees after the anchor cable body is locked;

b. the contact surface of the base plate and the pad pier is ensured not to have any gap;

c. cutting redundant anchor cable bodies of the anchor head by adopting a cold cutting method, wherein the reserved length outside the anchor is more than or equal to 5 cm;

d. when tension needs to be compensated, the tension length needs to be considered to be reserved;

e. the anti-corrosion treatment of the anchor head should be in compliance with the regulations.

8. The prestressed anchor cable construction method according to claim 1, wherein said step S8 of tensioning and locking is performed in accordance with the following process quality requirements:

a. leveling the support component surface of the bearing plate before tensioning, installing the bearing plate, the base plate and the anchorage device, keeping the bearing plate, the base plate and the anchorage device to be vertical to the axis direction of the anchor rod, and keeping the axis of the jack to be coincident with the axis of the anchor cable as much as possible when the jack is installed;

b. the jack and the high-pressure oil pump are calibrated before installation, tensioning is carried out according to calibrated data, and the working condition of the high-pressure oil pump and the smooth condition of an oil pipe are checked in advance so as to avoid tensioning failure caused by abnormal working of the oil pump during tensioning;

c. tensioning is carried out according to a certain program, and the tensioning sequence of the anchor cables is determined by considering the mutual influence on the adjacent anchor cables;

d. pre-tensioning the anchor cable for 2 times before formal tensioning, wherein the tensioning force is 0.1-0.2 times of the design load, so that the tight contact of all parts of the anchor cable and the flatness of the rod body are ensured, and the hidden deformation of the rod body is eliminated; when stretching is carried out after straightening, the starting point of the deformation amount is recorded by taking the state as a zero point;

e. controlling the tension control stress within the range of 0.65-0.75 times of the standard value of the anchor cable strength;

f. tensioning loads are applied step by step in a graded mode, the loads are increased to 1.05 times of design loads through the last tensioning, the loads are observed for 10-15 min, if deformation is unchanged, the anchor cable is kept in an original state, a pointer of a pressure gauge on the oil pump does not return, the design loads can be unloaded, and locking operation is carried out;

g. the locking operation must be strictly performed according to the standard, and after the anchor cable is locked by using a standard anchorage device, if obvious prestress loss is found, tensioning compensation is performed.

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